Leaf Micromorphology Aids Taxonomic Delineation within the Hypervariable Genus Metrosideros (Myrtaceae) on O\u27ahu

Variation in leaf micromorphology can aid delimitation of taxonomically difficult groups. The woody genus Metrosideros (Myrtaceae) dominates Hawai\u27i\u27s native forests and comprises striking, predominantly infraspecific, macromorphological variation, including many forms unrecognized in current taxonomic treatments. On taxonomically rich O\u27ahu, 10 taxa (varieties or unnamed morphotypes of M. polymorpha and other species) occur in a predictable sequence with overlapping ranges from low to high elevation along the numerous leeward ridges of the Ko\u27olau Range. We used scanning electron and light microscopy to examine mature, nonsenescing sun leaves from each of these 10 taxa. Parametric and nonparametric tests were used to compare stomatal complex (SC) traits and those of a newly described secretory structure (SS) across taxa. Correlations among traits and discriminant analyses were also done. Density and length of SCs were inversely related overall, and both measures varied significantly across taxa. Although abaxial SSs were consistently present only in the two highest-elevation glabrous taxa, adaxial SSs were present in all 10 taxa. Length and density of adaxial SSs and density of abaxial SSs varied across taxa, and densities of both SCs and SSs were greatest at high elevation. Combined, the SC and SS traits differentiated 100% of four glabrous varieties and two of three pubescent varieties of M. polymorpha. Variation in leaf micromorphology, including presence and density of a newly described SS, aids delimitation of closely related Hawaiian Metrosideros taxa and may refilect differential local adaptation across a heterogeneous landscape

Developing reading-writing connections; the impact of explicit instruction of literary devices on the quality of children's narrative writing

The purpose of this collaborative schools-university study was to investigate how the explicit instruction of literary devices during designated literacy sessions could improve the quality of children's narrative writing. A guiding question for the study was: Can children's writing can be enhanced by teachers drawing attention to the literary devices used by professional writers or “mentor authors”? The study was conducted with 18 teachers, working as research partners in nine elementary schools over one school year. The research group explored ways of developing children as reflective authors, able to draft and redraft writing in response to peer and teacher feedback. Daily literacy sessions were complemented by weekly writing workshops where students engaged in authorial activity and experienced writers' perspectives and readers' demands (Harwayne, 1992; May, 2004). Methods for data collection included video recording of peer-peer and teacher-led group discussions and audio recording of teacher-child conferences. Samples of children's narrative writing were collected and a comparison was made between the quality of their independent writing at the beginning and end of the research period. The research group documented the importance of peer-peer and teacher-student discourse in the development of children's metalanguage and awareness of audience. The study suggests that reading, discussing, and evaluating mentor texts can have a positive impact on the quality of children's independent writing

Repeated summer drought and re-watering during the first growing year of oak (Quercus petraea) delay autumn senescence and bud burst in the following spring

Climate change predicts harsher summer droughts for mid-latitudes in Europe. To enhance our understanding of the putative impacts on forest regeneration, we studied the response of oak seedlings (Quercus petraea) to water deficit. Potted seedlings originating from three locally sourced provenances were subjected to two successive drought periods during the first growing season each followed by a plentiful re watering. Here, we describe survival and phenological responses after the second drought treatment, applying general linear mixed modeling. From the 441 drought treated seedlings 189 subsisted with higher chances of survival among smaller plants and among single plants per pot compared to doubles. Remarkably, survival was independent of the provenance, although relatively more plants had died off in two provenances compared to the third one with mean plant height being higher in one provenance and standard deviation of plant height being higher in the other. Timing of leaf senescence was clearly delayed after the severe drought treatment followed by re-watering, with two seedlings per pot showing a lesser retardation compared to single plants. This delay can be interpreted as a compensation time in which plants recover before entering the subsequent developmental process of leaf senescence, although it renders seedlings more vulnerable to early autumn frosts because of the delayed hardening of the shoots. Onset of bud flush in the subsequent spring still showed a significant but small delay in the drought treated group, independent of the number of seedlings per pot, and can be considered as an after effect of the delayed senescence. In both phenological models significant differences among the three provenances were detected independent from the treatment. The only provenance that is believed to be local of origin, displayed the earliest leaf senescence and the latest flushing, suggesting an adaptation to the local maritime climate. This provenance also displayed the highest standard deviation of plant height, which can be interpreted as an adaptation to variable and unpredictable weather conditions, favoring smaller plants in drought-prone summers and higher plants in more normal growing seasons

Water status and yield response to deficit irrigation and fertilization of three olive oil cultivars under the semi-arid conditions of Tunisia

Sustainability of olive production is possible by adopting the modern techniques of irrigation and fertilization. In Tunisia, olive trees are usually cultivated in poor soils, under semi-arid conditions characterized by water scarcity. This study investigated the effects of different water supply and fertilization on leaf water status and crop yield of three different olive oil varieties cultivated in central Tunisia, during four experimental seasons (2014-2017). Three treatments were examined: trees conducted under rainfed conditions (TRF), which represented the control treatment, trees irrigated with 50% ETc (T50) and, finally, trees irrigated with 50% ETc and with additional fertilization (T50F). Leaf water content and potential, yield and water use efficiency have been monitored on three different varieties, Chetoui, Chemlali, and Koroneiki, which are quite typical in the considered region. For all the growing seasons, midday leaf water potentials were measured from April to September. Midday leaf water potentials (MLWP) were generally higher for the two irrigated treatments (T50 and T50F) than for non-irrigated trees (TRF). As the season proceeded, MLWPs tended to decrease during summer for all the treatments and varieties. The lowest values were observed for the non-irrigated trees, varying between -3.25 MPa to -4.75 MPa. Relative leaf water content followed the same trends of midday leaf water potentials. Chetoui showed the lowest yield, which did not exceed 1530 Kg/(ha year), even for irrigated and fertilized trees. On the other hand, the yields of Chemlali and Koroneiki, cumulated in the four years, reached the maximum value of about 20 tons/ha. For these two varieties, the cumulated yield obtained in the control treatment (TRF) resulted significantly lower than the corresponding of the other two treatments (T50 and T50F). The highest irrigation water use efficiency (WUE) was estimated for Chemlali (T50) and (TRF). WUE was equal to 1.22 Kg/m3 for Koroneiki under fertigated treatment (T50F). Application of the only water supply (50% ETc) or associated with fertilizer improved the tree water status and increased the productivity of Chemlali and Koroneiki varieties

Genome-wide analyses of cassava Pathogenesis-related (PR) gene families reveal core transcriptome responses to whitefly infestation, salicylic acid and jasmonic acid.

BACKGROUND:Whiteflies are a threat to cassava (Manihot esculenta), an important staple food in many tropical/subtropical regions. Understanding the molecular mechanisms regulating cassava's responses against this pest is crucial for developing control strategies. Pathogenesis-related (PR) protein families are an integral part of plant immunity. With the availability of whole genome sequences, the annotation and expression programs of the full complement of PR genes in an organism can now be achieved. An understanding of the responses of the entire complement of PR genes during biotic stress and to the defense hormones, salicylic acid (SA) and jasmonic acid (JA), is lacking. Here, we analyze the responses of cassava PR genes to whiteflies, SA, JA, and other biotic aggressors. RESULTS:The cassava genome possesses 14 of the 17 plant PR families, with a total of 447 PR genes. A cassava PR gene nomenclature is proposed. Phylogenetic relatedness of cassava PR proteins to each other and to homologs in poplar, rice and Arabidopsis identified cassava-specific PR gene family expansions. The temporal programs of PR gene expression in response to the whitefly (Aleurotrachelus socialis) in four whitefly-susceptible cassava genotypes showed that 167 of the 447 PR genes were regulated after whitefly infestation. While the timing of PR gene expression varied, over 37% of whitefly-regulated PR genes were downregulated in all four genotypes. Notably, whitefly-responsive PR genes were largely coordinately regulated by SA and JA. The analysis of cassava PR gene expression in response to five other biotic stresses revealed a strong positive correlation between whitefly and Xanthomonas axonopodis and Cassava Brown Streak Virus responses and negative correlations between whitefly and Cassava Mosaic Virus responses. Finally, certain associations between PR genes in cassava expansions and response to biotic stresses were observed among PR families. CONCLUSIONS:This study represents the first genome-wide characterization of PR genes in cassava. PR gene responses to six biotic stresses and to SA and JA are demonstrably different to other angiosperms. We propose that our approach could be applied in other species to fully understand PR gene regulation by pathogens, pests and the canonical defense hormones SA and JA

Variable selection for BART: An application to gene regulation

We consider the task of discovering gene regulatory networks, which are defined as sets of genes and the corresponding transcription factors which regulate their expression levels. This can be viewed as a variable selection problem, potentially with high dimensionality. Variable selection is especially challenging in high-dimensional settings, where it is difficult to detect subtle individual effects and interactions between predictors. Bayesian Additive Regression Trees [BART, Ann. Appl. Stat. 4 (2010) 266-298] provides a novel nonparametric alternative to parametric regression approaches, such as the lasso or stepwise regression, especially when the number of relevant predictors is sparse relative to the total number of available predictors and the fundamental relationships are nonlinear. We develop a principled permutation-based inferential approach for determining when the effect of a selected predictor is likely to be real. Going further, we adapt the BART procedure to incorporate informed prior information about variable importance. We present simulations demonstrating that our method compares favorably to existing parametric and nonparametric procedures in a variety of data settings. To demonstrate the potential of our approach in a biological context, we apply it to the task of inferring the gene regulatory network in yeast (Saccharomyces cerevisiae). We find that our BART-based procedure is best able to recover the subset of covariates with the largest signal compared to other variable selection methods. The methods developed in this work are readily available in the R package bartMachine.Comment: Published in at http://dx.doi.org/10.1214/14-AOAS755 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

The 4.2 ka event in the vegetation record of the central Mediterranean

In this paper, the variation in forest cover in the central Mediterranean region, reflected by percentage changes in the arboreal pollen record, has been examined in relation to the 4.2 ka event. A total of 36 well-dated and detailed pollen records from latitudes between 45 and 36 degrees N were selected and their vegetation dynamics between 5 and 3 ka examined in relation to the physiographic and climatic features of the study area and to the influence of human activity on past vegetation, as suggested by anthropogenic pollen indicators. We have found that the sites located between 43 and 45 degrees N do not show any significant vegetation change in correspondence with the 4.2 ka event. Several sites located on the Italian Peninsula between 39 and 43 degrees N show a marked opening of the forest, suggesting a vegetation response to the climate instability of the 4.2 ka event. Between 36 and 39 degrees N, a forest decline is always visible around 4.2 ka, and in some cases it is dramatic. This indicates that this region was severely affected by a climate change towards arid conditions that lasted a few hundred years and was followed by a recovery of forest vegetation in the Middle Bronze Age. Human activity, especially intense in southern Italy, may have been favored by this natural opening of vegetation. In Sardinia and Corsica, no clear change in vegetation is observed at the same time. We suggest that during the 4.2 ka event southern Italy and Tunisia were under the prevalent influence of a north African climate system characterized by a persistent high-pressure cell

Selenium supplementation for the primary prevention of cardiovascular disease

Background: Selenium is a key component of a number of selenoproteins which protect against oxidative stress and have the potential to prevent chronic diseases including cardiovascular disease (CVD). However, observational studies have shown inconsistent associations between selenium intake and CVD risk; in addition, there is concern around a possible increased risk of type 2 diabetes with high selenium exposure. Objectives: To determine the effectiveness of selenium only supplementation for the primary prevention of CVD and examine the potential adverse effect of type 2 diabetes. Search methods: The following electronic databases were searched: the Cochrane Central Register of Controlled Trials (CENTRAL) (Issue 10 of 12, October 2012) on The Cochrane Library; MEDLINE (Ovid) (1946 to week 2 October 2012); EMBASE Classic + EMBASE (Ovid) (1947 to 2012 Week 42); CINAHL (EBSCO) (to 24 October 2012); ISI Web of Science (1970 to 24 October 2012); PsycINFO (Ovid) (1806 to week 3 October 2012); Database of Abstracts of Reviews of Effects (DARE), Health Technology Assessment Database and Health Economics Evaluations Database (Issue 4 of 4, October 2012) on The Cochrane Library. Trial registers and reference lists of reviews and articles were searched and experts in the field were approached. No language restrictions were applied. Selection criteria: Randomised controlled trials on the effects of selenium only supplementation on major CVD end-points, mortality, changes in CVD risk factors, and type 2 diabetes were included both in adults of all ages from the general population and in those at high risk of CVD. Trials were only considered where the comparison group was placebo or no intervention. Only studies with at least three months follow-up were included in the meta-analyses, shorter term studies were dealt with descriptively. Data collection and analysis: Two review authors independently assessed trial quality and extracted data. Study authors were contacted for additional information. Main results: Twelve trials (seven with duration of at least three months) met the inclusion criteria, with 19,715 participants randomised. The two largest trials that were conducted in the USA (SELECT and NPC) reported clinical events. There were no statistically significant effects of selenium supplementation on all cause mortality (RR 0.97, 95% CI 0.88 to 1.08), CVD mortality (RR 0.97, 95% CI 0.79 to 1.2), non-fatal CVD events (RR 0.96, 95% CI 0.89 to 1.04) or all CVD events (fatal and non-fatal) (RR 1.03, 95% CI 0.95 to 1.11). There was a small increased risk of type 2 diabetes with selenium supplementation but this did not reach statistical significance (RR 1.06, 95% CI 0.97 to 1.15). Other adverse effects that increased with selenium supplementation, as reported in the SELECT trial, included alopecia (RR 1.28, 95% CI 1.01 to 1.62) and dermatitis grade 1 to 2 (RR 1.17, 95% CI 1.0 to 1.35). Selenium supplementation reduced total cholesterol but this did not reach statistical significance (WMD - 0.11 mmol/L, 95% CI - 0.3 to 0.07). Mean high density lipoprotein (HDL) levels were unchanged. There was a statistically significant reduction in non-HDL cholesterol (WMD - 0.2 mmol/ L, 95% CI - 0.41 to 0.00) in one trial of varying selenium dosage. None of the longer term trials examined effects on blood pressure. Overall, the included studies were regarded as at low risk of bias. Authors’ conclusions: The limited trial evidence that is available to date does not support the use of selenium supplements in the primary prevention of CVD